Known as a semiconductor device used as a power module used for a motor control and an inverter of an air conditioner, for example, is a semiconductor device including a heatsink, a heat radiation insulating substrate joined to the heatsink, a semiconductor element disposed on the heat radiation insulating substrate, and an insert electrode for connecting the semiconductor element to an external electrode.
A nut is disposed on an inside of the insert electrode, and a bolt can be screwed from an outside of the insert electrode (that is to say, an outside of the semiconductor device). The inside of the insert electrode, the nut, and the semiconductor element, for example, are sealed with a sealing resin.
When there is a slight gap between the insert electrode and the nut at a time of resin sealing (also referred to as a resin molding), the resin enters the gap. Then, an intrusion of the resin between the insert electrode and the nut occurs after the resin sealing.
The intrusion of the resin between the insert electrode and the nut causes a creeping of the resin at a time of tightening the bolt. The creeping of the resin causes a reduction in axial force while in use or right after tightening the bolt. The reduction in axial force may seriously degrade an assumed quality of the power module. Thus, the prevention of the intrusion of the resin is a significantly important factor in performing the resin sealing.
Known as techniques of temporarily fixing an insert electrode and a nut at a time of resin sealing are a technique of providing a resin plate to tighten a bolt and a technique of temporarily fixing the nut magnetically. However, the above techniques have a problem that an attachment force between the nut and the insert electrode is weak, so that a gap occurs, and a dissolved resin enters the gap. A technique of temporarily fixing a nut in a rotational direction is known (refer to Patent Document 1).